This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Annexin A2, a 38-kDa protein of the Ca2+-dependent phospholipid-binding annexin family, contains F-actin binding sites in its carboxyl domain. F-actin aggregation is enhanced when AnxA2 is incubated with withaferin A, a natural compound found in solanaceous plants [1]. At the cellular level, withaferin A has been shown to inhibit angiogenesis and metastasis [1, 2]. These findings make annexin A2 a potential drug target. We discovered a new crystal form of anxA2 with a monoclinic spacegroup P21 that diffracted to 2.30 [unreadable]. Previously, the structure of anxA2 was determined from crystals with orthorhombic spacegroup P212121 and resolution of 2.59 [unreadable] (PDB code: 1XJL). Despite the differences in crystallization conditions and spacegroup, superposition of the C(alpha) backbone of both structures results in a RMSD value of 0.43 [unreadable]. Both crystals have two molecules in the asymmetric unit, although the total number of calcium ions is different (old: 2x7, new: 2x3). Access to the putative withaferin binding site (Cys133) may be more obstructed in the new crystal form due to packing. Current efforts are focused on cocrystallization of anxA2 with withaferin A.